The present invention relates to component packaging. More particularly, the present invention relates to a redundant package for isolating optical components (e.g., arrayed waveguide gratings) from external stresses.
Fiber optic communication links have been conventionally employed in long-haul, point-to-point networks with controlled environments at all interface points. Such highly controlled, xe2x80x9ccentral officexe2x80x9d surroundings usually offer relatively benign operating environments (temperature, humidity, mechanical) for components. Consequently, highly functional components could be developed and installed without considering the impact of other, more extreme environments.
Recent technological advances, coupled with increasing bandwidth demand, are rapidly expanding the use of fiber optic components beyond the xe2x80x9ccentral officexe2x80x9d and into potentially harsher environments. For example, dense wavelength division multiplexing (DWDM) enables the transmission of multiple, independent wavelength streams across a single fiber. Predictably, this capability has resulted in the requirement to add or drop these optical channels along the previously untapped long lengths of fiber (and outside of the central office environment) to provide access to the individual wavelength streams. Optical add/drop multiplexers (OADMs) are employed for this function, enabled by arrayed waveguide grating (AWG) components for filtering and forwarding individual wavelengths.
In addition to these technological advances, simple market forces are pushing fiber networks beyond central offices and into the diverse terrain of xe2x80x9cmetroxe2x80x9d markets. This ever-increasing need for bandwidth which only fiber can deliver is resulting in the widespread deployment of fiber networks, and their associated components, into the harsher, less environmentally controlled conditions present in the metro market.
The demands placed on component designers now reach far beyond optical performance, and into the realms of thermal and mechanical insulation. Certain qualification standards (e.g., Telcordia) exist for reliability of optical components, and many customers require qualification under these standards. AWGs however are thin, fragile chips with narrow waveguides produced using planar lightwave circuit (PLC) processing techniques. The various processing tolerances required to meet the requisite optical specifications are already very tight, and in fact get tighter as the need to process more and closer channels increases. It is difficult and costly to impose yet additional requirements on the chip process in the form of advanced materials, processing techniques, etc. to satisfy the harsher environmental standards discussed above.
Environmentally secure packages therefore now play a vital role in the widespread commercialization of these devices. Without adequate packaging, components such as AWGs, with their highly unique and useful functions, would be relegated to laboratory environments only.
What is required, therefore, are advanced packaging techniques to enable the widespread use of otherwise fragile optical components in diverse and often stressful environments.
These requirements are met, and further advantages are provided, by the present invention which in one aspect is an optical component package having a first, inner package enclosing the optical component, and a second, outer package enclosing the inner package. A heater may be disposed in the inner package proximate the optical component to control the temperature thereof, and to maintain this temperature control, the outer package forms an isolated sealed airspace around the inner package. This isolated airspace thermally insulates the AWG device environment from the outside ambient environment. The thermal isolation reduces the power consumption required to maintain tight temperature control of the device and reduces thermally induced mechanical stresses which could negatively affect the device performance or reliability. These parameters are critical to the commercial viability of the device. The outer package is formed of a material having low thermal conductivity, to promote this insulating function.
The heater may be formed of a material having a coefficient of thermal expansion substantially matched to that of the optical component, to minimize thermal differences and the resultant stresses at the interface between these elements.
The inner package, in one example, is formed from a base, a heater affixed to the base, and the optical component is affixed to the heater. Sidewalls are affixed to the base around the heater, and a lid is affixed over the sidewalls.
This package is especially useful if the optical component comprises a planar lightwave circuit (PLC), e.g., an arrayed waveguide grating (AWG), which requires tight temperature control and structural integrity to maintain the integrity of the optical paths.